After taking Afrin, Turkish president says Ankara will continue army operation further east, where US army has presence.

Turkey has vowed to expand its operation in Syria's Afrin region to other Kurdish-held areas further east, prompting fears for a possible confrontation with US troops stationed in the area.

President Recep Tayyip Erdogan announced Turkey's plans to extend the operation a day after Turkish-led forces entered the city of Afrin in northwestern Syria virtually unopposed.

"We will continue this process until we entirely eliminate this corridor, including in Manbij, Ayn al-Arab, Tal Abyad, Ras al-Ayn and Qamishli," the Turkish leader said.

Turkey, together with the opposition Free Syrian Army (FSA) rebels, launched a military operation into Afrin region in January to vanquish the US-backed Kurdish People's Protection Units (YPG) fighters, which it deems "terrorists" near its border.

Expanding Turkey's military campaign into the much larger Kurdish-held territory further east would risk confronting troops of a NATO ally, the United States, that are deployed alongside a YPG-dominated force in northern Syria.

Turkish authorities have described the stretch of northern Syria under Kurdish control as a "terror corridor" on the long southern border.

The YPG has been Washington's main ally against the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) in Syria, in a partnership that has infuriated Turkey.

US criticism

Pentagon spokesman US Army Colonel Rob Manning reiterated Washington's criticism on Turkey's operation in Afrin in a press briefing on Monday.

"We are very concerned about the effect that fighting there [in Afrin] has had" on efforts to defeat ISIL, he said.

Meanwhile, Turkish presidential spokesperson Ibrahim Kalin said that Ankara and Washington had reached a general agreement on Manbij and that the Turkish side is now waiting for its NATO ally to implement the deal.

Ankara considers the Kurdish Democratic Union Party (PYD) in Syria and its armed-wing YPG to be "terrorist groups" with ties to the banned Kurdistan Workers' Party (PKK).

The PKK has waged a decades-long armed fight against the Turkish state that has killed tens of thousands of people.

The YPG had come to control large swaths of northern Syria, including Afrin, in the course of the seven-year Syrian war.

It gained the territory after defeating the ISIL group while fighting in a US-backed rebel alliance called the Syrian Democratic Forces (SDF).

Erdogan also said in his speech on Monday that Turkey would carry out an offensive against Kurdish fighters in northern Iraq if Baghdad does not clear the region of them, referring to the PKK presence there.